The existence of a dietary requirement for fatty acids of the Omega3 or Alpha-linolenic acid family remains an unsolved issue in human and animal nutrition. Like the Omega6 or linoleic acid family, Omega3 fatty acids are an important component of membrane lipids but cannot be synthesized by animals. The high content of Omega3 fatty acids in the retina and cerebral cortex suggests an important role in the function of neuronal and photoreceptor membranes. This point is emphasized by their strong specific incorporation and retention in these tissues. Recent studies of dietary deficiency of Omega3 fatty acids in rats demonstrated tissue depletion of Omega3 fatty acids, accompanied by reduced electrophysiological responsiveness of the retina and impaired learning ability. The applicability of these findings to higher mammals is untested. We propose to test the effects of a dietary deficiency of Omega3 fatty acids in nonhuman primates, using biochemical, electrophysiological, and behavioral techniques. Rhesus monkeys will be fed two semipurified diets: one, with fat supplied by safflower oil, will have a low content of Omega3 fatty acids and a high proportion of Omega6 fatty acids; the second, control diet, with fat supplied by soybean oil, will have a relatively high content and proportion of Omega3 fatty acids. Adult females will receive these diets for four months before mating and throughout pregnancy. Their infants will continue on similar diets from birth to one year. The levels of Omega3, Omega6, and Omega9 fatty acids in plasma lipids, erythrocytes, and skin biopsies will be monitored monthly. Retinal function will be evaluated with rod and cone electroretinograms and behavioral tests of vision, and learning ability will be tested in a reversal learning task. At one year, tissues--including cerebral cortex and cerebellum, retina, skeletal musclem cardiac muscle, aorta, liver, adrenals, ovary or testis, skin, and adipose tissue--will be examined for lipid and fatty acid content and for historlogical changes. Our objective is to determine in a primate model the existence and nature of a dietary requirement for Omega3 fatty acids.